Suppose you want to extrude a region the same size as the default cube -- in other words, one Blender unit on a side.

Undo your previous extrude by pressing Ctrl + Z .

Activate the extrude tool again by using E (or Mesh → Extrude Region).

This time, as you're moving the extruded vertices around, hold down the Ctrl key. You'll see that the new vertices will only move in multiples of a Blender unit. This is called snapping, and it makes it easy to extrude by exactly one blender unit. The size of the snapping depends on the zoom level; if you are zoomed out a long way from the object the snapping will be done in large increments and if you are zoomed in close you can snap in finer amounts.

Continue extruding until you have five cubes of equal size stacked atop one another. This will be one leg of your figure.

Another way to extrude by exactly one Blender unit is to press 1key while the tool is active.

If you press 2key when no tool is active, Blender will switch to the second layer, and your (first-layer) object will disappear. To make it visible again, press 1key .

If you are not using Front Ortho view, the blender unit will be much larger than the cube. Switching to that view will allow for the proper size, although you can manually enter the extrusion as 0.4 units.

Don't extrude any cube more than a unit at a time. You'll want those extra vertices, edges and faces later in this tutorial.

If the mesh gets too big for your view, you can zoom out using SCROLL or NUM−

Adjust the cursor position in orthographic top, front and side views ( Num7 , Num1 , and Num3 respectively) until the 3D cursor is about where the center of the head should be. It may help to use Shift + S → Snap → Cursor to Grid.

Make sure you're in Edit Mode with a 3D View window active. (If you create the head in Object Mode, it will be a separate object from the body, and changes to the body later in this tutorial won't affect the head.)

Create a sphere using Shift + A → Mesh → Icosphere.

Leave the default settings for subdivisions and size in the bottom left of the screen. (Note: Your computer may slow down if you set subdivisions above 6)

You should now have a small sphere at the top of the body. To make it more proportional to the body, resize it using the scale tool:

Make sure you're still in Edit Mode, with a 3D View window active and the head selected.

If necessary change the pivot point to Median Point.

Activate the scale tool by pressing S (or Mesh → Transform → Scale).

Move the mouse pointer until the head is the size you want.

You may also adjust its position using the grab tool:

Make sure you're still in Edit Mode, with a 3D View window active and the head selected.